The received signal quality is important for communications systems. Especially in known location measurement systems, the reference base station signal quality is essential for a location measurement unit (LMU). Location measurement systems are based on measuring base station signals and time delays between them. The greatest problem in these systems is the quality of the measured signals. Multipath propagation presents a problem in terms of signal timing determination reliability in spread-spectrum and GSM environments. Typically, a signal is transmitted from a base station (BTS) and can be reflected from a number of surfaces, such as buildings, mountains or trees. The timing determination is also interfered by for example adjacent channel radio signals.
Different solutions for improving the quality of the received signals have been proposed. One known solution is to combine the reference base station transmitter signal from a base station test connector with a suitable attenuator and a combiner. However, all base stations do not have test connectors. Furthermore, the combiners represent an additional component whose manufacture and installation expenses may grow high. Another existing solution is to take a transmitter signal from a base station transmitter EMP (Electromagnetic Pulse Protector) protector or use additional Directional Coupler. The EMP protector is used to protect the equipment against lightning strikes or high voltages coming down the centre conductor of the antenna line. The use of the EMP protector or additional coupler, however, requires a combiner. Also, shutting off the transmission during installation is necessary. Another solution for improving the signal quality is to move a radio frequency antenna to a better position for good reception of the reference base station. However, that is not always possible due to zoning regulations or physical objects. There are also different solutions of leaking cables, in which the transmitter signal is feeded to tunnels; these solutions would not provide sufficient coupling for the LMU requirements. An ideal solution would be to couple the transmitter signal from the transmitter cable directly to an LMU receiver antenna cable without any changes in the transmitter radio frequency lines.